Systems and methods for preparation of highly reactive alkali metal dendrites for the synthesis of organolithium reagents

ABSTRACT

Systems and methods for formation of highly reactive alkali dendrites are provided. For example, in some embodiments alkali metals are dissolved in ammonia to form metal electrides after which the ammonia is removed via vacuum to reveal highly activated metal surfaces in the form of crystalline alkali dendrites. The alkali dendrites can mimic powders but have the advantage of being freshly prepared from inexpensive and readily available metal sources. These uniquely activated metals exhibit enhanced reactivity comparatively to similar off the shelf sources of the corresponding metals. For example, the dendrites can have about 100 times greater surface area than conventional metal sources and/or be about 19 times more reactive than powders that serve as the industry standard for the preparation of organometallic compounds. After surface activation, these metals can be used to prepare various organometallic reagents.

CROSS REFERENCE TO RELATED APPLICATION

The present disclosure claims priority to and the benefit of U.S.Provisional Application No. 63/390,753, entitled “Preparation of HighlyReactive Lithium Metal Dendrites,” filed on Jul. 20, 2022, the contentof which is incorporated by reference herein in its entirety.

GOVERNMENT RIGHTS

This invention was made with government support under Grant No.DBI-0116835 awarded by The National Science Foundation. The governmenthas certain rights in the invention.

FIELD

The present disclosure relates to systems and methods for formation ofhighly reactive alkali dendrites, and more particularly relates to thesurface activation of alkali metals with ammonia for synthesis oforganometallic reagents.

BACKGROUND

Lithium (Li) metal has revolutionized many scientific arenas from thedevelopment of active pharmaceuticals to Li-batteries. Specifically, thephysical form of the Li-metal can greatly impact its chemical propertiesand function as most processes take place at the Li-metal surface. Aperson skilled in the art will recognize that Li-metal can be highlymalleable and can be shaped into various workable forms such as pellets,rods, and foils. Although these physical forms of Li-metal find use inmany real-life settings, the increased demand for faster electrontransfer properties in several industrial applications has resulted in agreat deal of investigation into Li-sources that vary in surface areaand composition. For instance, one of the most significant advances inthe chemical sciences involved the development of Li-powders for thepreparation of organolithium compounds which continue to providesolutions to many pressing synthetic challenges to this day.

Commercial sources of lithium metal routinely provide avenues for thesynthesis of many organometallic reagents. Technical aspects of suchreactions can impede everyday synthetic operations on both small andlarge scale reactions, and have several shortcomings. For example, FIG.1A illustrates a prior art process for using Li-metal to constructcarbon-lithium bonds. In the realm of organometallic chemistry, thetransfer of electrons from a metal to an organic substrate is thequintessential process to form carbon-metal bonds. However, because thereactions are heterogeneous, variabilities in the quality and area ofthe metal surface can often render these processes unpredictable andfacetious in nature especially on routine laboratory scales.Historically, reaction development in this field has relied onactivating the metal by mechanically reducing the size of the metalparticle and by the addition of chemical activators such as iodine toclean the metal surface.

Currently, commercial access to Li-powders or dispersions has becomeextremely limited as lithium's broad impact and future potential in theenergy and battery sector has shifted production lines of raw materialsto other areas.

Moreover, processes for the preparation of lithium powder (dispersion),which is the widely used source of lithium for application, are obtainedby physical means, while heating the alkali metal at a temperature aboveits melting point, and dispersing the molten metal in mineral oil,making the overall process unsafe and impracticable in most academicsettings. For example, in the 1970s, Rieke pioneered an elegant solutionto these practical problems of efficiency and generality for severalalkaline earth and transition metals such as magnesium, zinc, and copperby developing a method that allowed access to highly reactive metalpowders via the reduction of metal salts with alkali metals, as shown inFIG. 1B. One shortcoming of lithium, however, is that Li-metal bears thelowest reduction potential among the elements and therefore cannot beprepared using Rieke's method.

Accordingly, there is a need for development of systems and methods forformation a highly reactive lithium-metal source that mimics lithiumpowders but has the advantage of being freshly prepared from inexpensiveand readily available lithium sources.

SUMMARY

The present application is directed to systems and methods for formationof highly reactive alkali dendrites. Formation of these dendrites canresult from dissolving alkali metals in ammonia. For example, in someembodiments, a lithium-rod can be dissolved in liquid ammonia to formmetal electrides. Once formed, the ammonia can be removed to synthesizea new lithium-metal source. In some embodiments, the new lithium-metalsource can be in the form of crystalline lithium-dendrites having highlyactivated metal surfaces. These uniquely activated metals can exhibitenhanced reactivity comparatively to similar off the shelf sources ofthe corresponding metals. For example, these lithium-dendrites can haveabout 100 times greater surface area than conventional lithium-sourcescreated by prototypical mechanical activation methods. Concomitant withthe surface area increase, the lithium-dendrites are 19 times morereactive than lithium-powders which are currently the industry standardfor the preparation of organolithium compounds. After surfaceactivation, these metals can be used for efficient synthesis of variousorganometallic reagents, can serve as reducing agents, or any chemistrytraditionally associated with alkali earth metals. In some embodiments,the presently disclosed methods can allow for preparation of variousfamilies of organometallic reagents utilizing the described metals.

Other objects, features and advantages of the present disclosure willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating specific embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

This disclosure will be more fully understood from the followingdetailed description, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1A is a prior art illustration of a reaction for generatingmetal-carbon bonds;

FIG. 1B is a prior art illustration of a reaction for activation ofmetal for metal-carbon bond formation;

FIG. 2A is an example reaction of the present embodiments for forminglithium (Li)-dendrites from Li-ammonia solutions;

FIG. 2B is a photograph of a Li-rod used in the reaction of FIG. 2A;

FIG. 2C is a photograph of an electride formed as a result of thereaction of FIG. 2A;

FIG. 2D is a photograph of the Li-dendrites formed from the electride ofFIG. 2C via the reaction of FIG. 2A;

FIG. 2E is a photograph of the Li-dendrites of FIG. 2D in a flask;

FIG. 2F is another example reaction of the present embodiments forforming alkali dendrites;

FIG. 3A is a photograph that compares the surface areas of 500milligrams of each of the Li-rod, Li-foil, Li-powder, and the Lidendrites;

FIG. 3B is a scanning electron microscopy (SEM) image of Li-dendrites ofFIG. 2D at 60× magnification;

FIG. 3C is a SEM image of Li-dendrites of FIG. 2D at 250× magnification;

FIG. 3D is a SEM image of Li-dendrites of FIG. 2D at 500× magnification;

FIG. 3E is a SEM image of Li-powder at 1100× magnification;

FIG. 4A is a reaction and table showing kinetic measurements carried outby rapidly injecting a hexane solution of isopropanol (3.0 mmol) intoLi-metal (2.0 mmol) suspensions in hexanes;

FIG. 4B is a reaction and table evaluating experiments conducted over arange of reaction scales and their corresponding yield percentages;

FIG. 4C is a graph illustrating the reactivity of the compounds of FIG.3A following the reaction of FIG. 4A;

FIG. 5 is a table illustrating preparation of various organolithiumreagents and their use in further transformations.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. Thisincludes in the description and claims provided for herein. Further, oneor more examples of these embodiments are illustrated in theaccompanying drawings. Those skilled in the art will understand that thedevices and methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present disclosure is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present disclosure.

The present disclosure generally relates to systems and methods for thepreparation of highly reactive alkali dendrites with highly activatedsurfaces from alkali metals. At least one novel aspect of the presentdisclosure provides systems and methods for the activation of Li-metalthat furnishes a crystalline material with highly increased reactivity.One exemplary method of the present embodiments can use liquid ammoniato dissolve Li-metal to furnish a new Li-metal source in the form ofcrystalline Li-dendrites. The processes by which the Li-metal reacts toform the Li-dendrites are discussed in detail below. The Li-dendritescan have approximately 100 times greater surface area than conventionalLi-sources created by prototypical mechanical activation methods.Moreover, these Li-dendrites can be highly reactive and mimic Li-powderswhile having the advantage of being freshly prepared from inexpensiveand readily available Li-sources. After surface activation, these metalscan be used to synthesize organometallic reagents. These families oforganometallic reagents can, in some embodiments, be used for synthetictransformations of various compounds.

FIGS. 2A-2D illustrate an example reaction for the formation ofLi-dendrites that can be plated and/or crystallized from Li-ammoniasolutions in greater detail. As shown in FIG. 2A, synthesis ofLi-dendrites from bulk Li-material, e.g., Li-metal, and ammonia caninvolve a two-step process. First, the low reduction potential oflithium can be leveraged by creating a chemical equilibrium which wouldallow for Li-metal to be briefly ionized to a Li-cation and electride.FIGS. 2B-2C illustrate example embodiments of the Li-metal and theelectride, respectively. As shown, the Li-metal can include a Li-rod 10,though in some embodiments, a Li-foil can be used. The low reductionpotential of Li can allow for it to be easily ionized in the presence ofstrongly Lewis basic ligands such as ammonia or alkylamines. Forexample, the Li-rod 10 can be condensed in liquid ammonia to form thelithium electride. During this type of dissolution process, the selectron from Li-metal can be ionized into solution which can lead tothe characteristic blue hue of a solvated electron under relativelydilute conditions and a fiery bronze color at high concentrations. Anexample of the alloy, e.g., the Li-bronze compound or solution 12, isshown in FIG. 2C.

The ammonia used in the reaction of FIG. 2A can be manufactured annuallyon megaton scales making it an inexpensive and ideal solvent for bothacademic and industrial settings. Although it is a gas at standardatmospheric temperatures and pressures, its enthalpy of vaporization(23.35 KJ/mol at room temperature (rt)) is high, making it simple tocondense and easy to handle in liquid form. In some embodiments, 0.5 gLi-metal/13 mL was found to dissolve at −78 ° C. in anhydrous ammonia tocreate a Li-bronze solution. The temperature of −78 ° C. can be kept andmaintained substantially constant throughout the addition of liquidammonia to the metal alloy followed by slow stirring of the bronzesolution. The solution can then be allowed to reach room temperature(after all the ammonia is added) while being stirred at a constant rateto evaporate small amounts of ammonia.

Once formed, the electride can be followed by the microscopic reverse toreform the metal in a more reactive state. That is, after warming toroom temperature along with vigorous stirring, the ammonia can slowly beremoved in vacuo at 0.05 ton to remove substantially all of the liquidammonia present in the alloy to reveal highly activated metal surfaces.For example, in some embodiments, an amount of the ammonia removed fromthe alloy can be in approximately a range of about 99% to about 100%with respect to a total amount of the ammonia in the alloy, or inapproximately a range of about 99.5% to about 100% with respect to atotal amount of the ammonia in the alloy. It will be appreciated that insome embodiments trace amounts of lithium amide may be left behind asknown to one skilled in the art. For example, in some embodiments, whenthe ammonia is removed, a metallic Li-mirror can be gradually depositedon the walls of the vessel. Upon further evaporation, e.g., about 10-15min, of ammonia, metallic Li-dendrites 14 can begin to grow, forming thesemicrystalline material, as shown in FIG. 2D. After the removal ofexogenous ammonia via vacuum for about 0.5 h, the Li-dendrites 14 can beused immediately or easily removed, collected, weighed, and/or storedunder inert atmospheres, e.g., inert argon atmospheric conditions,without significant damage to the surface or morphology of the material.It will be appreciated that it may be important to avoid contaminationof the lithium sources to oxygen as it will reduce the reactivity of thedendrites. Moreover, this process can be reproducible and scalable up toat least 200 mmol where similar Li-dendrites were observed, as discussedin greater detail below. The ability to prepare a highly activated metalsurface at the beginning of each reaction can provide the opportunity tohave a better yield and provides a controlled process where conventionalprocesses fail. As shown in FIG. 2E, the Li-dendrites 14 can resembleLi-mirrors or crystals that are formed on a flask in which they arecontained upon the removal of ammonia from Li-electride solutions.

A novelty of the instantly disclosed systems and methods for thepreparation of highly reactive alkali dendrites relies on reversibilityof electride formation. Formation of electride solutions being areversible process may be unexpected as these solutions can be unstable.Moreover, the reactions that use alkali metal dendrites produce desiredresults in the absence of nearly all protic compounds to yield thedesired products in target amounts. Because ammonia is a proticcompound, it can be an unexpected result to one skilled in the art thathighly reactive alkali dendrites may be prepared from ammonia as thepresence of ammonia may conventionally be thought to inhibit the desiredreaction.

FIG. 2F illustrates an alternate example reaction for the formation ofLi-dendrites from Li-ammonia solutions. For example, while the methodsof the present embodiments are discussed with respect to formation ofLi-dendrites, in some embodiments, this general reaction can be appliedto other alkali metals, such as sodium and potassium. As shown in FIG.2F, the reaction can include a sodium or potassium metal being dissolvedin liquid ammonia in lieu of lithium. This dissolution can create anelectride that forms a Na-dendrite or a K-dendrite in accordance withthe reaction discussed above with respect to lithium.

Solvents other than ammonia can also be used in the reaction of thepresent embodiments. Some non-limiting examples of such solvents caninclude Hexmethylphosphoramide (HMPA) and/or different degrees ofamines, among others. These solvents can be used with Li-metal,Na-metal, and/or K-metal, among others.

The ability to dissolve alkali metals provides the unique ability tocreate a highly activated and clean surface of the alkali dendrite afterthe removal of ammonia. Specifically, the metallic state of theLi-dendrites of the present embodiments after formation can exhibit aclean surface as compared to that of other Li-metals. Moreover, thesurface area of the Li-dendrites 14 of the present embodiments can besignificantly greater than the surface areas of the off-the-shelf Li-rod10, Li-foil 16, and/or Li-powder 18 discussed herein. FIG. 3Aillustrates a comparison of the surface areas of Li-rod 10, Li-foil 16,Li-powder 18, and Li-dendrites 14 with a quarter used as a point ofreference. As shown, Brunauer-Emmett-Teller (BET) surface areameasurements of the Li-dendrites (115,000 cm²/g) revealed that thematerial has, on average, about 100 times higher surface area than theLi-powder (1,100 cm²/g), and in some embodiments about 105 times highersurface area than the Li-powder. This increased surface area can allowthe Li-dendrites 14 of the present embodiments to be used in a varietyof applications, such as lithium-ion batteries, preparation oforganolithium compounds, and other technical advances that utilizelithium. To gain insight into the surface morphology of the Li-dendrites14, a sample for scanning electron microscopy (SEM) can be randomlyselected and carefully mounted under inert atmospheres.

FIGS. 3B-3E illustrate comparison images of the Li-metals at variousmagnifications. Although the bulk morphology can be agglomerated in adendritic form, for example, the SEM images of the Li-dendrite acrossmagnifications, as shown in FIGS. 3B-3D, can show that themicrostructure can include non-porous crystals in the range of about20-100 μm in diameter. Moreover, the crystals can exhibit significantamounts of screw and step dislocations which can be attributed tonucleation being disturbed during the ammonia removal process. Furtherstill, a comparison of the microstructure of the Li-dendrites toLi-powder, with the Li-powder shown in FIG. 3E, showed that themorphology of the Li-powder can be spherical with no significantcrystalline features.

EXPERIMENTS Kinetic Analysis of Li-Metal in Various Physical Forms

A comparison of reactivity of synthesized Li-dendrites 14 to Li-metal inother physical forms can be performed via kinetic analysis. FIGS. 4A-4Cillustrate the results of this comparison in greater detail. Toestablish the kinetic behavior, isopropanol can be added separately tohexane suspensions of lithium rod, foil, powder, and dendrites, as shownin the reactions of FIGS. 4A-4B, or injected as a hexane solution ofisopropanol (3.0 mmol) into Li-metal (2.0 mmol) suspensions in hexanes,such that the evolution of hydrogen gas can be visually monitored byvideo recording using a burette. It will be appreciated that theexperiments with these suspensions can be conducted over a range ofreaction scales under identical conditions to generate the resultstabulated in FIGS. 4A-4B. This analysis can reveal sigmoidalconcentration versus time curves for the rod, foil and dendrites, asshown in FIG. 4C. To allow for a straightforward comparison, the rate ofhydrogen formation can be measured through the linear region of eachcurve. In some embodiments, the rate of hydrogen formation can be firstmeasured with curve (A) of the Li-rod (2.08 ±0.05)×10⁻⁴ M/s (A) so thatthe rates can be normalized. While lithium rod 10 and lithium foil 16both resulted in near identical reaction rates in curve (A) and curve(B), respectively, Li-powder 18 in curve (C) was about 10.5 times fasterthan the Li-rod 10. Unexpectedly, the Li-dendrites 14 (curve (D)) canexhibit a reactivity of about 199 times more reactive than the rod(curve (A)), and about 19 times faster than the Li-powder 18 (curve(C)), as shown in FIG. 4C. These higher reactivity values candemonstrate that the Li-dendrites 14 can provide a superior reactionsurface over the other Li-metal sources. Moreover, not only was theoverall reaction faster with the Li-dendrites 4, but the inductionperiod can be significantly reduced over the induction period of eitherof the Li-rod 10 and foil 16. This increase in reactivity rate can bedue to the combination of clean and increased surface areas as well asthe high densities of dislocations and imperfections which are canaccelerate rates of electron transfer.

Synthesis of Reagents with Li-Dendrites

In some embodiments, the Li-dendrites can be highly reactive towardoxidative addition reactions with organic halides allowing access to awide variety of organolithium species that previously could only beprepared with Li-powders. The protocol to activate the Li-metal can beperformed over a range of reaction scales allowing for fresh batches ofactivated Li-metal to be prepared. The preparation of alkali metals oralloys, e.g., Li-dendrites 14, with highly activated surfaces canprovide a technical advance by affording a metal source that allows forvarious efficient synthesis of organometallic reagents on varyingscales. Organolithium reagents synthesized with the Li-dendrites of thepresent embodiments can exhibit superior yields than conventionalsources of lithium metal. For example, in some embodiments, yields canbe improved by about 5% to about 25% as compared to organolithiumreagents synthetized with conventional sources of lithium metal. It willbe appreciated that while the present disclosure discusses organolithiumreagents, other organo-alkali metal reagents, e.g., organosodium and/ororganopotassium, can be synthesized with the techniques of the presentdisclosure.

FIG. 5 illustrates preparations of organolithium reagents and use infurther transformations via use of various compounds, e.g., organichalides, in greater detail. For example, the Li-dendrites 14 of thepresent embodiments can leverage their increased reactivity tosynthesize organometallic reagents on various scales, e.g., small,medium, and even large scales. For example, the volume of theLi-dendrites can allow for minute amounts of Li-metal to be reliably andaccurately weighed affording reproducible results even on small scales,which is often challenging for Li-insertion reactions. Moreover, theactivated surfaces allow for the preparation of many organometallicreagents that are traditionally challenging to prepare by any othermeans, such as lithiated ethers 22 and 23.

As noted above, in some embodiments the Li-dendrites can be highlyreactive toward reductive insertion reactions with organic halidesallowing access to a wide variety of organolithium species thatpreviously could only be prepared with Li-powders. Moreover, theenhanced reactivities of the Li-dendrites 14 can be used to develop asimple protocol for the preparation of organolithium reagents. To testthe feasibility of the outlined reductive metalation, s-BuCl can beselected as the model substrate because its rate of Li-metal insertionis known to be in between that of n-BuCl and t-BuCl making it ideal forreaction optimization. After an extensive survey of the reactionconditions, s-BuLi was found to be able to be produced in 87% yieldemploying 4.0 equivalent of Li-dendrites along with 1 mol% of sodium ona 2.5 mmol scale. The addition of sodium (−1 mol%) as well as theemployment of multiple equivalents of Li-metal can be vital forreasonable rates of Li-insertion to be achieved and prevent deleteriouselimination and or dimerization pathways.

Effect of Li-Metal Source on the Rate of Metalation with s-BuCl. Giventhe rate enhancement observed toward hydrogen evolution, a similar rateenhancement may be observable with reductive metal insertion reactions.For example, to establish the kinetic relationship between Li-powders 18and Li-dendrites 14, s-BuCl solutions in pentane can be separately addedto suspensions containing either the Li-dendrites 14 or Li-powder 18.Subsequent tracking of the s-BuCl concentration over time can allow fora direct comparison of the two materials. During such tracking, theLi-dendrites 14 can be found to have initiated and completely consumedthe halide starting material in less time (about 300 s) than theLi-powder 18 usually can take to initiate. Further, upon fitting thelinear region bearing constant k_(obs) the Li-dendrites 14 can insert atleast about 6.2 times faster than the Li-powder 18. These resultstogether can indicate that the Li-dendrite 14 would be ideally suitedfor applications that require faster or more predictable initiationrates.

A person skilled in the art will recognize that evaluation of thereliability and scalability of the optimized protocol can be performedover a range of reaction scales that are common practice in thesynthetic laboratory, e.g., 0.1, 2.5, 10 and 50 mmol scales. As shown inFIG. 5 , compounds such as n-BuLi could be readily prepared incomparable yields in a safer non-flammable poly(a-olefin) SpectraSyn™2,further highlighting the robustness of the formation of the Li-dendritesof the present embodiments. Moreover, with reference to FIG. 5 , methylchloride 2, neopentyl chloride 3, and trimethylsilylmethyl chloride 4can result in high yields (86-94%). Although primary alkyl bromides 5and 6 can be found to give the desired insertion reaction in excellentyields (>91%), the secondary alkyl bromide substrate 8 can result inslightly lower yield (63%) emphasizing that secondary bromide leavinggroups offer avenues for nonproductive E2-elimination pathways to becomecompetitive. Next, for a set of halocarbocycles (9-12), the reaction canproceed smoothly with the corresponding Li-carbocycle being formed inmoderate to good yields (65-86%). A slight modification may be neededfor the 5- and 6-membered halocarbocycles whereby tert-butyl methylether (TBME) can be identified as a sacrificial additive to preventunproductive consumption of the organic halide. This method can befurther applied to the synthesis of tertiary alkyl lithium reagents,which can be difficult to access using previously reported Li-insertionreactions on laboratory scales. Like the 5- and 6-membered ring systems,t-BuCl 13 can benefit greatly from the addition of TBME (77% vs. 45%without). Norbornyl chloride 14, on the other hand, can display moderateyields (72%) and show no improvement with TBME, consistent with TBME'srole in the suppression of E2-elimination.

To broaden the utility of the Li-dendrite system, a series of vinyl andaryl chlorides can also be used. For example, after a solvent change todiethyl ether, 1-chlorocyclohexene 15 can result in good yields of thevinyl lithium reagent. Further, chlorobenzene 16, 4-chlorotoluene 17,4-chloroanisole 18, and 4-chlorodimethylaminobenzene 19 can result inexcellent yields (91-96%). Moreover, aryl bromide 20, a substrate knownto undergo facile side reactions from lithium halogen exchange, can befound to afford its corresponding aryl lithium in excellent yields(92%). By investigating the aryl halide substrate scope, somelimitations, such as strongly electron deficient arenes, e.g.,4-chlorobenzotrifluoride 21, can be observed to be completely unreactiveunder the presently described conditions.

To further establish the versatility of the methods of the presentdisclosure, preparation of organolithium compounds can bear functionalgroups that are often incompatible with alkyl lithium reagents such ast-BuLi, which may be the only viable option for complementary Li-halogenexchange processes. Notably, ethers can be often susceptible to faciledeprotonation reactions with strong organolithium bases, and this limitstheir applications in synthesis. Accordingly, chloroarene 22 that bearsboth alkylether and tetrahydrofuran functional groups can undergoLi-insertion cleanly and efficiently. Moreover, primary alkyl chloride23 incorporating an alkylether subunit can undergo smooth conversioninto its organolithium, highlighting the robustness of our Li-source tocreate disconnections that have been employed in the synthesis ofbiologically relevant compounds.

Preparation of isotopically labeled n-Bu⁶ Li with Li-dendrites. It willbe appreciated that the ability to achieve high yields from Li-insertionreactions on small scales with short reaction times can be of greatsynthetic importance. The methods of the present embodiments can beuseful to synthesize ⁶ Li isotopically labeled organolithium reagentswhich can be used to obtain detailed aggregate structural information by⁶ Li NMR investigations. For example, the high yields and concentrationsobtained for n-Bu⁶ Li 24, a ubiquitous base can be used to prepare otherorganolithium congeners through Li-halogen exchange reactions, as shownin FIG. 5 . Several contemporary protocols for the synthesis of 24 canuse either the reduction of toxic diorganomercury compounds with ⁶Li-rod or costly syntheses on scales of >100 mmol for high yields andpurities to be achieved, which can exhibit several significantshortcomings over the instantly recited process.

In some embodiments, once the organolithium reagents discussed above areprepared, these reagents can be used in one or more synthetic settings.For example, the practical and synthetic advantages of Li-dendrites 14over other Li-sources in the synthesis of various organolithiumcompounds can be used in synthetic transformations as shown in FIG. 5 .In some embodiments, prototypical carbon-carbon bond forming processessuch as nitrile addition can perform well. Further, the alkylation of4-phenyl-1-bromobutane 6 can be simple, clean, and high yielding, e.g.,a yield of about 90% or more, with about 93% in some embodiments, whileemploying the freshly prepared cyano-Gilman reagent 28. Finally,potassium trifluoroborate 32, which is a common reagent employed inSuzuki-Miyaura cross-coupling reactions, can also be isolated in goodyields through trapping vinyllitihum 30 with trimethyl borate 31.

PROCEDURES Procedure for Measuring the Solubility of Lithium in Ammonia

In an argon atmosphere glovebox, a 250 mL Schlenk flask was charged withlithium metal rod (500.0 mg, 72.0 mmol), a glass-coated stir bar, andcapped with a septum. The flask was removed from the glovebox and placedunder argon atmosphere on a Schlenk line. The Schlenk flask was placedin a dry ice bath (−78 ° C.) at a low stirring rate. Amodified-graduated cylinder was placed under an argon atmosphere andsubmerged in a dry ice bath (−78 ° C.) until 13.0 mL of liquid ammoniawas condensed. Using a cannula transfer, liquid ammonia was added to theSchlenk flask containing the lithium metal. The solution can be stirredin a dry ice bath until all the lithium metal rod was completelydissolved and a dark purple/blue color was achieved.

General Procedure for the Preparation of Lithium Dendrites

In the glovebox, a 50 mL Schlenk flask was equipped with a glass-coatedstir bar, lithium (276 mg, 40.0 mmol), sodium (2.8 mg, 0.12 mmol, 1 wt%) and capped with a septum. The flask was removed from the glovebox andfreshly condensed NH₃ (8.0 mL, 5 M) was added at −78 ° C. via cannula.After about 5 min, the lithium bronze solution was warmed to roomtemperature over 20 min where ammonia in an amount of about 2.0 mLboiled off slowly. The vessel was placed under vacuum (0.05 torr) toremove the remainder of ammonia over 30 min. The flask was backfilledwith argon and returned to the glovebox. The lithium was removed bycarefully scraping the walls of the flask and pouring onto wax weighingpaper to furnish the lithium dendrites (265 mg, 95%) as a crystallinesolid. The lithium dendrites kept their luster for several weeks in asealed container in the glovebox though most were used within 24 h.

Procedure for Measuring the Rate of Hydrogen Evolution with VariousLithium Sources

In the glovebox, a 10 mL Schlenk flask was equipped with a glass-coatedstir bar, lithium (13.9 mg, 2.0 mmol, 1.0 equiv) and capped with aseptum. The flask was removed from the glovebox and hexane (2.0 mL) wasadded via syringe. The flask was lowered into a 35 ° C. bath and theflask was quickly vented to release excess pressure. The flask wasconnected to a burette with a water reservoir (colored with CuSO₄) andstirring (400 rpm) was started. Video recording was started, the flaskwas opened through the sidearm, and a solution of isopropanol (0.50 mL,3.0 mmol, 1.5 equiv, 6.0 M) in hexane was added rapidly via syringe.Recording of the reaction was continued until at least 14.0 mL of gashad been collected or 1 h had elapsed. Time points for every 0.50 mLwere then extracted by going frame by frame in the resulting videos andsubtracting the time from the end of the addition of IPA. The amount ofhydrogen evolved at each timepoint was used to calculate an effectiveconcentration of LiOiPr which was then plotted vs. time. The linearregion, following any induction period, was fit using the Curve FitterToolbox in Matlab. This procedure was performed in triplicate to obtainan average rate for each form of lithium, with results shown anddiscussed with respect to FIG. 4C above. Compiled kinetic data for theformation of LiOiPr using lithium rod, foil, powder and dendrites isshown in Table 1, below:

Entry Run k_(obs) (M s⁻¹) k_(avg) (M s⁻¹) k rel Rod 1 (1.92 ± 0.01) ×10⁻⁴ (2.08 ± 0.05) × 10⁻⁴ 1.0 2 (1.98 ± 0.07) × 10⁻⁴ 3 (2.33 ± 0.06) ×10⁻⁴ Foil 1 (2.46 ± 0.04) × 10⁻⁴ (2.71 ± 0.06) × 10⁻⁴ 1.3 2 (2.46 ±0.06) × 10⁻⁴ 3 (3.21 ± 0.07) × 10⁻⁴ Powder 1 (1.94 ± 0.06) × 10⁻³ (2.18± 0.09) × 10⁻³ 10.5 2 (2.37 ± 0.05) × 10⁻³ 3 (2.22 ± 0.13) × 10⁻³Dendrites 1 (4.18 ± 0.30) × 10⁻² (4.14 ± 0.25) × 10⁻² 199 2 (3.54 ±0.22) × 10⁻² 3 (4.69 ± 0.22) × 10⁻²

Procedure for Measuring the Rate of s-BuCl Consumption with VariousLithium

Sources

In the glovebox, a 10 mL Schlenk flask was equipped with a glass-coatedstir bar, lithium (69.4 mg, 10.0 mmol, 4.0 equiv) and capped with aseptum. The flask was removed from the glovebox and pentane (2.5 mL) wasadded via syringe. The flask was lowered into a 30° C. bath. After about5 min, a 1.0 mL stock solution containing s-BuCl (2.5 mmol, 1.0 equiv,2.5M) and octadecane (6.25 mmol, 0.25 equiv, 0.625 M) in pentane wasadded rapidly. Aliquots (30-50 μL) were withdrawn at the indicatedtimepoints and quenched by rapidly injecting them into test tubescontaining precooled (0° C.) water (3.0 mL). Each aliquot was extractedwith pentane (2.0 mL), filtered through sodium sulfate, and analyzed byGC-FID. Relative integrations to the octadecane standard were used tofind the s-BuCl concentration which was then plotted vs. time. Thelinear region, following any induction period, was fit using the CurveFitter Toolbox in Matlab. This procedure was performed in duplicate toobtain an average rate for both forms of lithium.

Procedures for the Preparation of Sec-Butyl Lithium on Alternate Scales

0.1 mmol scale: In the glovebox, a 1-dram vail was equipped with a stirbar, charged with lithium dendrites (2.8 mg, 0.40 mmol, 4.0 equiv), andcapped with a septum cap. The vial was removed from the glovebox andplaced in a preheated 37° C. bath. Pentane (0.40 mL) was added viasyringe and stirring was started. A solution of sec-butyl chloride (100μL, 0.1 mmol, 1 equiv, 1 M) in pentane was added dropwise over 5 min.The solution was stirred for 1 h. The solution was withdrawn via syringeand the vial was rinsed with pentane (2×100 μL). The combined pentanesolution was added to an NMR tube containing cyclooctadiene (8.3 mg,0.077 mmol). The yield was determined by a previously reported NMRmethod. Integration of the alkyllithium reagent (−0.98 ppm, 1H) relativeto the cyclooctadiene alkene signal (5.47 ppm, 4H) resulted in a ratioof integrals: 2.95:10 for a yield of 91%.

2.5 mmol scale: In the glovebox, a 10 mL Schlenk flask was equipped witha glass-coated stir bar, lithium (69.4 mg, 10.0 mmol, 4.0 equiv), sodium(0.7 mg, 0.03 mmol, 1 wt %) and capped with a septum. The flask wasremoved from the glovebox and freshly condensed NH₃ (2.0 mL, 5 M) wasadded at −78° C. via cannula. After about 5 min, the lithium bronzesolution was warmed to room temperature over 20 min where ammonia in anamount of about 0.5 mL boiled off slowly. The vessel was placed undervacuum (0.05 torr) to remove the remainder of ammonia over 30 minproviding lithium dendrites. The flask was backfilled with argon and theseptum was removed briefly about 10 s followed by carefully scraping thelithium dendrites off the walls to the bottom of the vessel with a metalspatula. The flask was lowered into a preheated oil bath at 37° C.Pentane was added (1.5 mL, 1 M) followed by the dropwise addition of asec-butyl chloride solution (1.0 mL, 2.5 mmol, 1.0 equiv, 2.5 M) over 60min with vigorous stirring. After a minimum of about 1 h after theaddition, the purple/black heterogeneous mixture was then withdrawn witha syringe and the remaining solids were washed with pentane (2×1.0 mL).The combined pentane solution was filtered through a Teflon syringefilter (Restek Cat#26142-248, 13 mm, 0.22 μm). The resulting solutionwas titrated following the modified Gilman's method described above toprovide 3.02 mL of a 0.70 M solution for an 87% yield.

10 mmol scale: In the glovebox, a 50 mL Schlenk flask was equipped witha glass-coated stir bar, lithium (276 mg, 40.0 mmol, 4.0 equiv), sodium(2.8 mg, 0.12 mmol, 1 wt %) and capped with a septum. The flask wasremoved from the glovebox and freshly condensed NH₃ (8.0 mL, 5 M) wasadded at −78° C. via cannula. After about 5 min, the lithium bronzesolution was warmed to room temperature over 20 min where ammonia about2 mL boiled off slowly. The vessel was placed under vacuum (0.05 torr)to remove the remainder of ammonia over 30 min providing lithiumdendrites. The flask was backfilled with argon and the septum wasremoved briefly after about 10 s followed by carefully scraping thelithium dendrites off the walls to the bottom of the vessel with a metalspatula. The flask was lowered into a preheated oil bath at 37° C.Pentane was added (6.0 mL) followed by the dropwise addition of asec-butyl chloride solution (4.0 mL, 10.0 mmol, 1.0 equiv, 2.5 M) over60 min with vigorous stirring. About 1 h after the addition thepurple/black heterogeneous mixture was then withdrawn with a syringe andthe remaining solids were washed with pentane (2×2.0 mL). The combinedpentane solution was filtered through a Teflon syringe filter (PALLPN#4927, 25 mm, 0.2 μm). The resulting solution was titrated followingthe modified Gilman's method described above to provide 12.89 mL of a0.69 M solution for an 89% yield.

50 mmol scale: In the glovebox, a 250 mL Schlenk flask was equipped witha glass-coated stir bar, lithium (1.388 g, 200.0 mmol, 4.0 equiv),sodium (13.9 mg, 0.60 mmol, 1 wt %) and capped with a septum. The flaskwas removed from the glovebox and freshly condensed NH₃ (40 mL, 5 M) wasadded at −78° C. via cannula. After 5 min, the lithium bronze solutionwas warmed to rt over 45 min where ammonia in an amount of about 8 mLboiled off slowly. The vessel was placed under vacuum (0.05 torr) toremove the remainder of ammonia over 60 min providing lithium dendrites.The flask was backfilled with argon and the septum was removed brieflyfor about 30 s followed by carefully scraping the lithium dendrites offthe walls to the bottom of the vessel with a metal spatula. The flaskwas lowered into a preheated oil bath at 37° C. Pentane was added (30.0mL) followed by the dropwise addition of a sec-butyl chloride solution(20.0 mL, 50.0 mmol, 1.0 equiv, 2.5 M) over 60 min with vigorousstirring. About 1 h after the addition the purple/black heterogeneousmixture was transferred via cannula to a frit containing celite and wasfiltered. The remaining solids were washed with pentane (2×10.0 mL)transferred via cannula to the celite pad. The resulting filtrate wastitrated following the modified Gilman's method described above toprovide 51.82 mL of a 0.87 M solution for a 91% yield.

General Procedure A for the Preparation of Organolithium Reagents

In the glovebox, a 10 mL Schlenk flask was equipped with a glass-coatedstir bar, lithium (69.4 mg, 10.0 mmol, 4.0 equiv), sodium (0.7 mg, 0.03mmol, 1 wt %) and capped with a septum. The flask was removed from theglovebox and freshly condensed NH₃ (2.0 mL, 5 M) was added at −78° C.via cannula. After about 5 min, the lithium bronze solution was warmedto rt over 20 min where ammonia in an amount of about 0.5 mL boiled offslowly. The vessel was placed under vacuum (0.05 ton) to remove theremainder of ammonia over 30 min providing lithium dendrites. The flaskwas backfilled with argon and the septum was removed briefly for about10 s followed by carefully scraping the lithium dendrites off the wallsto the bottom of the vessel with a metal spatula. The flask was loweredinto a preheated oil bath at 37° C. Solvent was added (1.5 mL, 1 M)followed by the dropwise addition of an organohalide solution (1.0 mL,2.5 mmol, 1.0 equiv, 2.5 M) over 60 min with vigorous stirring. After aminimum of about 1 h after the addition, the purple/black heterogeneousmixture was then withdrawn with a syringe and the remaining solids werewashed with solvent (2×1.0 mL). The combined solvent solution wasfiltered through a Teflon syringe filter (Restek Cat#26142-248, 13 mm,0.22 μm). The resulting solution was titrated by modifying a knownprocedure by Gilman.

A scintillon vial was charged with DI water (10 mL) and a magnetic stirbar followed by sparging with argon for 10 min. The vial was fitted witha septum and an aliquot of the organolithium reagent (0.50 mL) was addedin one portion. The solution was titrated with standard acid (HCl, 0.242M) using phenolphthalein as indicator (2-3 drops) to give the totalbase. A second 5 mL flask was equipped with a magnetic stir bar, cappedwith a septum, and purged. The flask was charged with diethyl ether (3mL) and 1,2-dibromoethane (200 μL). An aliquot of organolithium reagent(0.50 mL) was added dropwise with vigorous stifling. After about 5 min,DI water (2 mL) was added, and the solution was titrated with standardacid (HCl, 0.242 M) using phenolphthalein as indicator (2-3 drops) togive the residual base. The active base of the organolithium reagent wasthen calculated by subtracting the residual base from the total base.The yield of the organolithium reagent was determined using the volumeof the solution and concentration of active base. The volume of thesolution was calculated by measuring the mass and density prior totitration.

General Procedure B for the Preparation of Organolithium Reagents

In the glovebox, a 10 mL Schlenk flask was equipped with a glass-coatedstir bar, lithium (69.4 mg, 10.0 mmol, 4.0 equiv), sodium (0.7 mg, 0.03mmol, 1 wt %) and capped with a septum. The flask was removed from theglovebox and freshly condensed NH₃ (2.0 mL, 5 M) was added at −78° C.via cannula. After 5 min, the lithium bronze solution was warmed to rtover 20 min where ammonia in an amount of about 0.5 mL boiled offslowly. The vessel was placed under vacuum (0.05 torr) to remove theremainder of ammonia over 30 min providing lithium dendrites. The flaskwas backfilled with argon and the septum was removed briefly for about10 s followed by carefully scraping the lithium dendrites off the wallsto the bottom of the vessel with a metal spatula. The flask was loweredinto an ice bath at 0° C. Solvent was added (1.5 mL, 1 M) followed bythe dropwise addition of an organohalide solution (1.0 mL, 2.5 mmol, 1.0equiv, 2.5 M) over 15 min with vigorous stirring. After a minimum ofabout 30 min after the addition, the purple/black heterogeneous mixturewas then withdrawn with a syringe and the remaining solids were washedwith solvent (2×1.0 mL). The combined solvent solution was filteredthrough a Teflon syringe filter (Restek Cat#26142-248, 13 mm, 0.22 μm).The resulting solution was titrated as described above.

One skilled in the art will appreciate further features and advantagesof the disclosures based on the provided for descriptions andembodiments. Accordingly, the inventions are not to be limited by whathas been particularly shown and described. All publications andreferences cited herein are expressly incorporated herein by referencein their entirety.

Some non-limiting claims are provided below.

What is claimed is:
 1. A method of forming an alkali dendrite,comprising: combining an alkali metal with a solvent to form an alloy;and removing the solvent from the alloy to form a alkali dendrite. 2.The method of claim 1, wherein combining the alkali metal with thesolvent comprises dissolving the alkali metal in the solvent.
 3. Themethod of claim 1, wherein the alkali is lithium.
 4. The method of claim3, wherein the lithium is a lithium rod. The method of claim 1, whereinthe alkali is one or more of sodium or potassium.
 6. The method of claim1, wherein the solvent comprises liquid ammonia.
 7. The method of claim1, wherein the solvent comprises one or more of Hexmethylphosphoramide(HMPA) and different degrees of amines.
 8. The method of claim 1,further comprising keeping a temperature of the alloy substantiallyconstant during the combining step.
 9. The method of claim 8, furthercomprising stirring the alloy to evaporate an amount of the solvent fromthe alloy. The method of claim 9, wherein an amount of the solventremoved from the alloy can be in approximately a range of about 99% toabout 100% with respect to a total amount of the solvent in the alloy.11. The method of claim 1, wherein the solvent is removed by using avacuum.
 12. The method of claim 1, wherein a surface area of the alkalidendrite is about 100 times greater than a surface area of aconventional alkali powder.
 13. The method of claim 1, wherein a surfacearea of the alkali dendrite is about 2,950 times greater than a surfacearea of the alkali metal.
 14. The method of claim 1, wherein a bulkmorphology of the alkali dendrite is agglomerated in a dendritic form.The method of claim 1, wherein a reactivity of the alkali dendrite isabout 19 times greater than a reactivity of a conventional alkalipowder.
 16. The method of claim 1, wherein a reactivity of the alkalidendrite is about 199 times greater than a reactivity of the alkalimetal.
 17. The method of claim 1, further comprising reacting the alkalidendrite with an organic halide to form an organometallic reagent. 18.The method of claim 17, further comprising synthetically transformingthe organometallic reagent by alkylation to generate a yield of about90% or more
 19. An organo-alkali metal reagent synthesized using thealkali dendrite of claim
 1. A synthetically transformed compound formedfrom the organometallic reagent of claim 17.